Bubble-like “stars within stars” could explain the strangeness of a black hole

Black holes were once virtual monsters born in the tangled nest of Einstein's theory of general relativity, and are now known to be real celestial bodies like stars, moons and galaxies.

But make no mistake. Its engines are still as mysterious as they were when the German theoretical physicist Karl Schwarzschild was in charge First played with Einstein's field equations I came to the conclusion that space and time can wrinkle into pits of no return.

Physicists Daniel Jampolski and Luciano Rizzola of Goethe University Frankfurt have gone back to the first step in trying to better understand the equations that describe black holes, and have come up with a solution that is easier to imagine, if no less bizarre.

While conventional images of black holes contain a mess of contradictory physics at their centers, Jampolski and Rizzola have come up with a unique twist on a gravitationally bound “bubble” of matter, which could contain a whole series of interwoven bubbles within it.

“It is remarkable that even 100 years after Schwarzschild provided his first solution to Einstein's field equations from the theory of general relativity, new solutions can still be found.” He says Risola.

“It's a bit like finding a gold coin along a path that many others have discovered before.”

Black holes hide a dirty secret in physics. Insert enough objects into the space described by what is known as Schwarzschild radiusGravity will overcome all other forces and pull that mass into a much smaller space. So say the field equations in general relativity.

However, equations cannot really tell what happens at the other end of this great pressure. As we focus on ever smaller distances, quantum physics becomes increasingly important. With no easy way to connect the two (almost) everything-inclusive theories, we face a big question mark about what happens to matter when gravity crushes it beyond a certain point.

As if that wasn't enough of a challenge, the existence of objects that can send information on a round trip to the cosmic prison and evaporate in a constant glow of heat known as Hawking radiation represents a physical paradox, based on the rule that information cannot simply disappear.

In 2001Quantum physicist Paul Mazur and astrophysicist Emil Mottola collaborated to understand the equations to see if they could avoid these dead ends.

What they found was a gravitationally condensed star. Referred to eerily as a gravastar, this hypothetical construct describes a layer of matter compressed to an almost impossible degree of thinness, inflated from within with a generous helping of dark energy.

As strange as these star balloons sound, they will still look like black holes from the outside, while conveniently escaping the information paradox and avoiding the need for an infinitely thick twinge of quantum absurdity at their core.

Jampolski and Rizzola found that it was possible for a gravatar with a slightly thicker membrane to balance a second gravatar inside it. Likewise, the second nested gravatar could be pregnant with its strange shell composed of highly compressed material, forming what they call a nestar.

“The nestar is like a matryoshka doll,” He says Jampolski, who came up with the solution under Rizzola's supervision.

Inventing cosmic monsters outside the shadow cast by pure theory may seem strange, but that's how black holes were identified in the first place. More importantly, finding the limits of what the theory can suggest could lead to observations that solve the black hole's most vexing mysteries.

“Unfortunately, we still have no idea how to create such a gravastar.” He says Risola.

“But even if stars don't exist, exploring the mathematical properties of these solutions will ultimately help us understand black holes better.”

This research was published in Classical and quantum gravity.